Process for tanning



minum and chromium. Th

" producing good leathers.

Patented .ian. 28, i936 STATES 2,029,088 PROCESS F98 TANNING Harold G. Turley,

Somerville, Fox Chase, & Haas Company,

Moorestown, N. J., and Ian 0.

Pa, assignors to Riihm Philadelphia; Pa.

No Drawing. Application May 12, 1934,

Serial No.

13 Claims. (01. 149-5) This invention relates generally to an improved process for tanning raw hidesor skins and more particularly for the purpose of making white leather.

Raw skins or hides may be converted into leather in several diiferent, ways, depending on the type of leather'desired. In all cases the skins are first treated to remove the hair. This may be done in a variety of different ways, using lime, sodium sulfide, etc. During this process the leather-producing fibers are rendered soft and supple and satisfactory for making leather. The skins so prepared are then tanned, and this process may be carried. out in numerous diiferent ways. For instance, the tanning may be accomplished by the use of extracts ofthe vegetable tannins, in which case an excellent leather, generally of a brownish color is produced. Such leather, however, is not resistant to hot water.

The second method of tanning consists in the use of mineral salts, particularly those of alue aluminum salts may yield a white leather which, however, is not generally resistant to washing with,cold water nor to a short treatment with hot water. It is usually a thin fiat leather suitable for making gloves but less satisfactory for full? round shoe leathers. .When chromium salts are used a leather is obtained which is resistant to hot water and consequently this process is in very wide use, particularly on lightweight skins. On the other hand, such leather always. has 'a blue. or greenish blue color so that it is very diflicult to produce a good white color on this stock.

A third method of tanning which has found a'limited use consists in the application of aldehydes, particularlyv of formaldehyde. The leather produced by this method is white and does not break down on treatment with hot water. However, it is of a thin fiat character, absorbs water instantly and subsequently dries out so hard that it is unsuitable for many purposes.

Many materials prepared synthetically have been tried as tanning agents and are capable of However, such leathers have the same drawback as those made with vegetable tannins, namel hot water.

We have found that a good white leather having high resistance to both hot and cold water maybe madeby certain combinations oi! steps in the tanning process. It is an object 01' this invention to prepare a leather which is of unusually good quality with respect to color, feel, fullness, resistance to hot and cold water, and which after y, lack of resistanceto added are based on treatment with hot wate dries out soft and supple. It is a further object of this invention to prepare a white leather which does not discolor in light, which is free from any trace of a blue or brownish color, and which is white throughout. 5 It is another object of this invention to prepare a leather on which delicate shades and. bright colors may be produced. It is a further object to prepare a suede leather which has exceptionally ood color and water resistance anda very 1 smoothfnap. Other objects will appear hereinafter.

In carrying out our invention, the skins prepared for tanning are adjusted to a definite degree of acidity and a combination tannage is built up in a series of steps, each of which contributes its peculiar quality to the finished leather.

In this way a leather is obtained which is sur-' prisingly superior to that made according to any one of the individual steps of this particular combination tannage. plished by applying to the skins, at a definite degree of. acidity either successively or simultaneously, a suitable aldehyde, 2. salt of aluminum of a definite basicity and a synthetic tanning material. These tanning agents may be added to the leather successively in any order, or two may be used simultaneously, followed by the third, or all three may be used at the same time. Leather tanned in this way may be tatliquored and finished in any suitable manner. The following is our preferred method of carrying out this invention:

The skins are treated in th up to the pickled condition. pickled in a drum in a weak salt until they show a pH of approximately 4.5. To this same drum is then added 10% by weight of a 37%,;solutlon of formaldehyde, whereupon the drum is run for live hours and allowed to stand overnight. The percentages ofmaterials the pickled weight of the skins. An unusual feature of our invention is the discovery that the formaldehyde tannage may be carried out at a pH in the vicinity of the isoelectric point 45 of the hide protein. 0n the following day, a solution or alum of the proper basicity and concentration is added. The drum is run for live hours and again allowed to stand overnight. The alum solution contains from 1.25 to 2.25% of aluminum 5 oxide in the form of a 40% basic aluminum sulphate, the baslcity being calculated on the Schorlemmer, scale. Such a solution can be conveniently prepared by dissolving the proper amount of commercial aluminum sulphate, free 5 e customary way, They are then desolution of common Briefly, this is accom- 20 of iron salts, in water'and adding the calculated amount of a weak alkali, such as sodium bicarbonate, borax or soda ash. On the third day, the

and fatliquored with a suitable oil in the usual way. We have found that most of the commercial sulphonated oils recommended for use on white leather are suitable for the leather produced by our process. The skins are then hung up and allowed to dry slowly. The resulting leather is white throughout and very resistant to wetting but can bemoistened back slowly. These skins may be staked and finished in any desired manner. The leather obtained by this process is pure white and may be used as such or dyed to give any desired color. geous as a base for pastel shades. The skins may be dyed by any of the standard methods, using acid, direct or basic dyes, following which they may be fatliquored and finished as usual.

the same liquor, 10 lbs. of 37% formaldehyde so- Our invention may be illustrated by the following examples, but it is not limited to the specifie details since the invention may be otherwise practiced within the scope of the appended claims:

Example 1.- lbs. of pickledkidskins are placed in a small drum with 200 lbs. water and 10 lbs. common salt. Bicarbonate of soda is added in successive small amounts and the drum run until, the skins show a uniform pH of 4.5. To theskins in the same liquor is added 10 lbs. of formaldehyde (37%), the drum run 5 hours and then shut down overnight. Next day the drum is run l hour, then 100 lbs. of a solution containing 8 lbs. of sulfate of alumina (141-120) and 2%lbs. sodium bicarbonate is added. The drum is run 5 hours and then shut down overnight. Next day, the drum is run '1 hour, the liquor drained oil, and the skins washed for hour. 200 lbs. water containing 10 lbs. of a synthetic tanning material, made by condensing phenol sulphonic acid with formaldehyde is then added. This solution is adjusted to a pH of 4.5 before putting it in the drum. The drum is run for l hour,.the liquor drained off, the skins washed for A hour, fatliquored with 5 lbs. of sulfonated neats-foot oil and horsed up overnight. Nextjday, they are shaved if desired, and

hung to dry in a cool room, after which they are" processed according to the methods in. general use for'the treatment of skins which have been crusted, to yield a soft white leather of good grain and excellent fullness, which is notreadily wet with cold water and which will not shrink when treated with water as hot as F.

Example 2.-100 lbs. of pickled sheepskins are placed ina small drum with 100 lbs. of water and 10 lbs. common salt. Soda ash is added in successive small amounts. and the-drum run until the skins show a uniform pH of 4.75. .To the skins in lutionis then added, the drum run for 5 hours and then shut down overnight. Next day, the drum is run 1 hour, 100 lbs. wateris added, and a dry mixture of 15 lbs. sulfate of alumina (14Hz0) and 12 lbs. borax thrown in. The drum is run 5 hours and then shut down overnight.

"Next day the drum is run 1 hour, the liquor 10% of a commercial synthetic tan- It is particularly advantas.

drained off, and the skins washed for 4 hour. 200 lbs. water containing 18 lbs. of a synthetic tanning material prepared by the sulfonation of 4,4-dihydroxydiphenyldimethylmethane is added, the solution being adjusted to a pH of 4.5 prior to putting in the .drum. The drum is run 1 hours, the liquor drained ed, the skins washed for hour, fatliquored with 10 lbs. of

sulfonated cocoanut oil and horsed up overnight.

Next day they are tacked in the wet' state. dried in a. cool room, and finished up in the customary way.

Example 3.-lo0 lbs. of pickled calfskins are placed in a small drum with 200 lbs. water and 10 lbs. of. common salt. Bicarbonate of soda is added in successive small amounts until the skins show a uniform pH of 5.0. To the skins'in the.

synthetic tanning material prepared by condens-- ing naphthalene sulfonic acid with formalde hyde and adjusted to pH 4.5 is then added. The

drum is run for 1 hour, the liquor drained,ofi,. the skins washed for 4, hour and then horsed up overnight. Next day, they are set out, shaved, washed for A hour and fatliquored with 3 lbs. of a sulfonated blend of neats-foot, cocoanut, and sperm oils. When this oil is almost all taken up by the skins, 1 lb. of titanium oxide dispersed in warm water is added and the drum run' A;

hour longer. The skins are then hung to dry in a cool room, and processed later in.the customary way. 7

Example 4.-l00 lbs. of pickled calfskins are placed in a small drum and 200 lbs. of water and '10 lbs. common salt. Borax is added in successive small amounts and the drum run until the skins show a uniform pH of 4.25 to-4.5. This liq.-

nor is drained and 200 lbs. water added, 7 lbs. of a synthetic tanning material prepared by coupling benzidine disulfonic acid with a substituted aromatic sulfonyl chloride substantially asdescribed in U. S. Patent #1,938,022 is added. The drum is run 1 hour, 10 lbs. of formaldehyde (37% solution) added to the same liquor, the drum run Next day the drum is run 1 hour and 100 lbs.

of a. solution containing 15 lbs. sulfate of alumina (14H2O)- and 3 lbs. of soda ash added. The drum 5 hours, and shut down overnight.

is run 5 hours and shut down overnight. It is run 1 hour next day, the liquor drained oi, the skins washed for hour, then fatliquored with 4 lbs. of sulfonated cocoanut oil, and horsed up overnight. Next day, they are set out, shaved,

hung up and allowed to dry. The crusted skins are wet back slowly, staked and tacked, then bufied and brushed on the-flesh side to give a white suede leather of excellent, whiteness and possessing a fine nap. Y Example 5.--100 lbs. of pickled calfskins are placed in a small drum with 200 lbs. water and 10 lbs. common salt. Bicarbonate of soda is added in successive small amounts and the drum run until the skinsshow a uniform pH of 4.5. To

the same liquor is added 10 lbs. formaldehyde (37% solution), 14 lbs. of sulfate of alumina (141-1120), 11 lbs. borax, and 15 lbs. of a synthetic tanning material prepared by condensing naphthalene aulfonic acid with formaldehyde in the presence of salicylic acid, the complete solution beingadjustedtoa pHof-i.5. Thedrumisrun intermittently for 48 hours and the skins horsed up 24 hours. They are then set out, shaved, washed for it hour. and fatliquored with 4 lbs. of sulfonated olive oil. when the oil is almost all taken up by the skins, lbs. of English colloidal clay dispersed in warm water is added to the and this is run ta hour longer. The skins are then hung up, allowed-to dry in a cool room and processed later in the ordinary way.

Example 6.--100 lbs. of pickled califskins are processed in exactly the same way as the sheepsmns in mple 2, except that lbs. of synthetic' tanning material prepared by sulionation of the liquid resin formed by condensation of phenol with acetaldehyde, is added in place of the synthetic material used in Example 2.

i Example 754% lbs. of pickled caliskins are except that 8 lbs. of a synthetic tanning material prepared by condensing the sulfonation prt of tertiary amyl phenol with formaldehydein nce oi salicyclic acid and/or thiourea is added in place of the synthetic material used in Example 6.

Example 8--1G@ lbs. of pickled calfsmns are I placed in a Small drum with 100 lbs. water and 10 lbs. common salt. 5% 3 ash is added in successive small amounts and the drum run until the skins show a uniform pH of 4.75. To the skins in the same liquor is added to lbs. of formaldehyde (37% solution), the drum run 5 hours and thenv of soda is added in successive small portions,

n 5-. ng until the hides show auniform pH of $.75. 24 lbs. of formaldehyde, (37% solution),

is added and the drum run for 5 hours. 30 lbs. oi

sulfate of alumina (MHZQ) amide lbs. horns are then thrown in, and the drum run intermittently for hours. The skins are horsed up for two days, set out and shaved. washed /2 hour, 20 lbs. oi a synthetic tanning material as given in mample, adjusted to a pH of 4.5 is then added,

the drum is run 1 /2 hours, drained, and the smns washed /2 hour, and iatli uored with 6% of an oil made by sulfonation of a. blend of neats-foot, caster and cocoanut oils. The skins are horsed up overnight and crusted. After wetting back slowly, they are staked out and tacked, then bufied on the grain side to give a soft white imitation buckskin of excellent feel which is resistant to wetting with. cold water and will not shrink when treated with water. at 180 F.

Example 10.-300 lbs. of pickled calfskins are depiokledand tanned in the same manner as in Example 5. After the skins have been horsed up for 24 hours, they are divided into smaller lots and colored in several ways. (a) 100 lbs. are placed in 100 lbs. water at 120 F. and 1 lb. of Acid Leather Brown ER is added. The drum is run hour, the skins rinsed oflf with warm water and fatliquored-in the normal way. (b) 100 lbs. are placed in 100 lbs. water at 120 F. and 1 1b. of

-' in ely the same way as in Example run V5 hour, 1 lb. formic acid is added, and drumming is continued for ,5 hour. The skins are washed, iatliquored and finished up in the normal way. (0) 100 lbs. are placed in 100 lbs. water at 120 F. and /3 lb. of Basic Black A. cone. is

' added. Thedrumis run hour,theskinsrinsed oil and iatliquored in the normal way. In this way a rich full black color is secured which provides a pleasing contrast to the white leather obtained when no color is applied, and moreover shows a pure white cut.

Example 11.-100 lbs. oi pickled sheepskins are placed in a small drum with ZOO-lbs. water and 20 lbs. common salt. Bicarbonate of soda is added in successive small amounts and the drum run until the skins show a uniform pH of 4%4-5. To the skins in the same liquor is added 9 lbs. of crotonaldehyde, and the drum run intermittently for 24 hours. A mixture or 10 lbs. iron free aluminum sulfate and 8 lbs. borax is added and the drum. run 5 hours, then shut down overnight. The skins are thoroughly washed and the tannage then completed by application of a synthetic tan nlng material as in Example 1. In this way, a soft leather of excellent feel and a creamy white color is obtained.

Example 12. -1co pounds of pickled and decontinued for 5 hours and then shut down overnight. Next day the drum is run for 1 hour, liquor drained oil, and the skins washed for /2 hour. 200 pounds of water containing 5 pounds of a synthetic tanning material prepared by the mi lionation of d,4'-dihydroxydiphenyldimethylmethane is added. The drum is run 1 hours, the liquor drained off, the skins washed for hour, iatliquored with 15 pounds of a sulfonat'ed cocoanut oil, and horsed up overnight. Next day they are allowed to crust out. On staking and finishing in'the customary way, a soft, white glove leather is obtained.

' Many modifications and variations within the spirit of this invention will suggest themselves to those versed in the art. For instance, the nature of the raw' stock used may be varied from those specifically mentioned in the examples.

A complete tannage can also be secured, if desired, by reducing the amount of material used in any one step and compensating by an increase in the amount of the material used in either of the other steps. For instance, the formaldehyde may be reduced by /2 and the amount of alum or synthetic tanning material doubled. This is true the reagents but a balance must be maintained among them, based approximately on the amounts specified in the examples.

These processes are carried out at temperatures commonly used in tannery practice. It .is convenient to start with liquors at about 80 F. since this can be maintained ratherreadily at any season of the year. Formaldehyde tannage occurs more readily the higher the temperature but it 7 Direct Fast Brown TSL is added. The drum is is not good practice to exceed 80 F. in the early stages, or 110 F. in the later stages until after all the formaldehyde has been fixed in the skins. Although we prefer. in making a smooth grained leather, to apply the formaldehyde under the acid conditions described. yet, for some purposes, it is naturally obvious that the formaldehyde tannage can be carried out as is more customary; in an alkaline bath. The formaldehyde may be replaced by other suitable aldehydes, such as croton aldehyde. The alum can be adjusted to the desired basicity by various alkalies. It is preferably applied at the basicity of on the Schorlemmer scale. However. this may be reduced to a rather lower figure, say to 35, and may also be increased somewhat, say to 45. In the latter case, however, a complication is introduced owing to the low solubility of an alum of much higher'basicity than 40, when used at the dilutions normally employed in tanning. The amount of synthetic tanning material can be very greatly increased if desired even up to ten times the amount given in the examples. In such cases a softer and more mellow leather is obtained.

This process of tanning may be used toproeuce leathers of widely varying characteristics. As examples may be mentioned, side leather, calfskin, buckskin (genuine and imitation), suede, kidskin, sheepskin, glove, reptile, welting leather, etc. While primarily designed to make white leather which will have no trace of blue cast, and will show a white cut all the way through, this process is capable of use as a standard method of I making leather which can be colored to any shade .skin in any order. I

4. The step in the process of tanning which desired. However, its special merit lies in the fact that delicate shades of pure colors can be obtained because the leather has no color before applying the dyestufi's.

The leathers produced by this process are dis= tinctly difierent from those produced by other processes. In the first place, a white leather is obtained which is difi'erent from the darker colored leathers obtained by the use of vegetable and chrome tans. It has a considerably greater resistance to water than leathers made by the formaldehyde process, alum process or acombination of the two.

We claim:

1. The step in the process of tanning which comprises treating skins and hides withan aldehyde capable of reacting with the hide protein, a salt of aluminum and a synthetic organic tanning material.

2. The step in the process of tanning which comprises treating skins and hides which have been adjusted to a pH of 4.25 to 5.0 with an aldehyde-capable of reacting with the hide protein, a salt of aluminum and a synthetic organic tanning material.

3. The step in the process of tanning which comprises treating skins and hides. which have been adjusted to a pH of 4.25 to 5.0 with an aide-.- hyde capable of reacting with the hide protein, a

salt of aluminum and a synthetic organic tanning material, these agents being applied to the comprises treating skins and hides which have aoaaess been adjusted to a pH of 4.25 5.0 with an aldehyde capable of reacting with the hide protein. a

basic salt of aluminum and a synthetic organic tanning material.

5. The step in the process of tanning which comprises treating skins and hides which have been adjusted to a pH of 4.25 to 5.0 successively with formaldehyde, 9. salt of aluminum or about so% basicity, and a synthetic organic tanning material, these agents being applied to the skin in order.

6. The step in the process of tanning which comprises treating skins and hides which have been adjusted to a pH of 4.25 to 5.0 simultaneously with formaldehyde, a salt of aluminum of about 40% basicity, and a synthetic organic tanning material.

7. The step in the process of tanning which comprises treating skins and hides successively,

(A) with a mixture of two of the group consist ing of formaldehyde, a basic aluminum salt anda synthetic organic tanning material and (B) with the third member of the group. 4

9. step in the process of tanning which comprises treating skins and hides which have been adjusted to a pH 01 4.25 to 5.0 successively, (A) with a mixture of two of the group consisting of formaldehyde, a basic aluminum salt and a synthetic organic tanning material and (B) with the third member of the group, the two treatments taking place in either order.

l0. The step in the procem oi tanning which comprises treating skins and lLides which have been adjusted to a pH of 4.25 to 5.0 successively with croton aldehyde, a basic salt of aluminum and a synthetic organic tanning material, thwe agents being applied to the skin in any order.

11. The step in the process of tanning which comprises treating skins and hides which have been adjusted to a pH of 4.25 to 5.0 simultaneous- .ly with croton aldehyde, a basic salt of aluminum and a synthetic organic tanning material.

12. The step in the process of tanning which comprises treating skins and hides which have been adjusted to a pH of 4.25 to 5.0 successively with (A) a mixture of two of the group consisting of croton aldehyde, a basic salt of aluminum and a synthetic organic tanning material and (B) with the third member of the group, the two treatments taking place in either order.

3.3.The step in the process of tanning which I comprises treating skins and hides which have been adjusted to a pH of 4.25 to 5.0 successively with (A) a mixture of formaldehyde and a basic salt of aluminum, and with (B) a synthetic er= ganic tanning material, the two steps taking place in either order.

' ransom C. 

